In packaging machines that produce sealed cartons containing food products or liquids, the carton blanks are typically introduced to the machine from a magazine. The magazine usually holds a stack of carton blanks in a unerected and compressed state, and urges the carton blanks toward the gate portion of the magazine. The gate positions and holds the carton blanks so they can be picked one at a time by a mechanism that unfolds and erects the blanks to form cartons having side walls and unsealed top and bottom panels. After the bottom panel of the erected carton blank is sealed, a food product or a liquid can be received in the carton, the top panel of the carton can then be formed and sealed, and the filled and sealed carton can be dispensed from the packaging machine for eventual shipment to the consumer.
As the carton blanks are unfolded and erected by the mechanism that receives the individual carton blanks from the gate, the blanks can either be erected properly in a rectangularly-shaped manner or improperly in an L-shaped manner. A properly erected, rectangularly-shaped carton blank has substantially perpendicular adjacent side walls, and is capable of having its bottom panels properly folded and sealed so that the carton interior can be filled and the top panels properly folded and sealed. In an improperly erected, L-shaped carton blank, pairs of adjacent side walls are parallel (that is, the carton blank folds in on itself). Thus, the bottom panels in an improperly erected, L-shaped carton blank are not aligned for proper sealing, and the carton cannot therefore be filled and sealed reliably.